1. Field of the Invention
This invention relates to the field of portable, refrigerant recovery units.
2. Discussion of the Background
Portable, refrigerant recovery units are primarily used to transfer refrigerant from a refrigeration system to a storage tank. In this manner, the refrigerant can be removed from the system and captured in the tank without undesirably escaping into the atmosphere. Needed repairs or other service can then be performed on the system.
Such recovery units face a number of problems in making the transfer of the refrigerant to the storage tank. In particular, the initial pressures of the refrigerant in the system can be quite high (e.g., 100-300 psi or more). These pressures can exert significant forces on the components of the unit including the pistons and drive mechanism. In some cases, the initial force may even be high enough to overpower the drive mechanism of the recovery unit and prevent it from even starting. In nearly all cases, the forces generated by the incoming pressurized refrigerant during at least the early cycles of the recovery operation are quite substantial and can be exerted in impulses or jolts. These forces can easily damage and wear the components of the unit if not properly handled.
In some prior designs, attempts have been made to minimize the forces exerted on the piston by exposing both sides of the head of the piston to the pressurized refrigerant. However, nearly all of these prior designs result in exposing not only the underside of the piston head to the refrigerant but also the piston rod and drive mechanism (e.g., crankshaft). Because the refrigerant typically has oil and other contaminants (e.g., fine metal particles) in it, the exposed piston rod, crankshaft, other parts of the recovery unit can become prematurely worn and damaged, particularly at their seals and bearings.
In other prior arrangements that do not expose these parts of the unit to the refrigerant, efforts have been tried to minimize the wear and damage to the drive mechanism (e.g., crankshaft bearings) from the refrigerant forces by operating another piston along the crankshaft at 180 degrees out of phase. However, these arrangements still drive the piston rods eccentrically about the axis of the crankshaft and out of alignment with each other. In most cases, they also pivotally mount the piston heads to the piston rods (e.g., with wrist pins). Although the forces of the pressurized refrigerant on the crankshaft are somewhat offset in such arrangements, the eccentrically mounted and unaligned piston rods still apply unbalanced stresses to the crankshaft. Additionally, the forces of the pressurized refrigerant are still borne by the pivot arrangement between the head and rod of each piston. The pivot arrangement in particular can then wear leading to irregular operation of the piston and seal leakage. Eventually, the pivot arrangement may even fail altogether.
With these and other problems in mind, the present invention was developed.